CVE-2020-2168 in Azure Container Service Plugin
Summary
by MITRE
Jenkins Azure Container Service Plugin 1.0.1 and earlier does not configure its YAML parser to prevent the instantiation of arbitrary types, resulting in a remote code execution vulnerability.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 03/26/2020
The vulnerability identified as CVE-2020-2168 affects the Jenkins Azure Container Service Plugin version 1.0.1 and earlier, presenting a critical remote code execution risk through improper YAML parsing configuration. This flaw resides in the plugin's handling of YAML input data, which fails to restrict type instantiation during parsing operations. The vulnerability stems from the plugin's use of a YAML parser that allows arbitrary object instantiation without proper sanitization, creating a pathway for malicious actors to execute code remotely on affected Jenkins servers.
The technical implementation of this vulnerability involves the YAML parser's lack of type filtering mechanisms, which enables attackers to craft malicious YAML payloads containing references to arbitrary Java classes. When Jenkins processes these crafted inputs through the Azure Container Service plugin, the parser attempts to instantiate objects of types specified in the YAML, potentially loading and executing malicious classes from the classpath. This behavior aligns with CWE-502, which addresses deserialization of untrusted data, and represents a classic example of unsafe deserialization in Java applications. The vulnerability creates a direct attack surface where remote code execution becomes possible through carefully constructed YAML content that leverages the plugin's parsing functionality.
The operational impact of this vulnerability extends beyond simple remote code execution, as it provides attackers with full control over affected Jenkins instances. Once exploited, attackers can execute arbitrary commands with the privileges of the Jenkins process, potentially leading to complete system compromise. The vulnerability affects Jenkins environments that utilize the Azure Container Service plugin, making it particularly concerning for organizations that rely on containerized deployment workflows. The remote nature of the exploit means that attackers can target vulnerable systems from outside the network perimeter, eliminating the need for local access or network reconnaissance. This makes the vulnerability especially dangerous in cloud environments where Jenkins instances are exposed to public networks.
Mitigation strategies for CVE-2020-2168 require immediate action to upgrade the affected Jenkins Azure Container Service plugin to version 1.0.2 or later, which includes proper YAML parser configuration to prevent arbitrary type instantiation. Organizations should also implement network segmentation to limit access to Jenkins servers, restrict plugin installations to only necessary components, and conduct thorough security reviews of all installed plugins. The remediation process should include disabling the affected plugin if it is not actively required, implementing strict input validation for all YAML processing, and monitoring for suspicious activity that might indicate exploitation attempts. Additionally, organizations should consider implementing principle of least privilege for Jenkins user accounts and ensuring that Jenkins instances are not exposed to untrusted networks. This vulnerability demonstrates the importance of secure coding practices around deserialization and input processing, particularly in enterprise automation platforms like Jenkins that handle sensitive configuration data. The ATT&CK framework categorizes this vulnerability under T1059 for command and scripting interpreter, as the exploitation results in command execution capabilities, and T1210 for exploitation of remote services, given the remote attack surface provided by the plugin functionality.